ALLJOYN-1836 subtask ALLJOYN-1837 updated pinvoke with new function name

This is a temporary update so that the change for ALLJOYN-1837 will not break
break the Unity Extension.  This calls the new alljoyn_busobject_signal()
function.  The CancelsessionlessMessage was added to AllJoyn C binding but.
This change does not add the CancelsessionlessMessage to the Unity Extension
that will be done for ALLJOYN-1838 another subtask of ALLJOYN-1836.

Change-Id: Ia860ce0cad44f114763aba62b4571694255b69a1
ALLJOYN-1249: Place files associated with C++ in a dist/cpp folder

Separating the C++ files into there own folder makes the SDK distribution
simpler to understand for developers.

Install the Unity Documentation in DISTDIR